linux-kernel - Re: [PATCH 4/4] iommu: Introduce guest PASID bind function

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Message-ID: <20190920163843.GD1533866@lophozonia>
Date:   Fri, 20 Sep 2019 18:38:43 +0200
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Jonathan Cameron <jic23@...nel.org>
Subject: Re: [PATCH 4/4] iommu: Introduce guest PASID bind function

On Wed, Sep 18, 2019 at 04:26:34PM -0700, Jacob Pan wrote:
> Guest shared virtual address (SVA) may require host to shadow guest
> PASID tables. Guest PASID can also be allocated from the host via
> enlightened interfaces. In this case, guest needs to bind the guest
> mm, i.e. cr3 in guest physical address to the actual PASID table in
> the host IOMMU. Nesting will be turned on such that guest virtual
> address can go through a two level translation:
> - 1st level translates GVA to GPA
> - 2nd level translates GPA to HPA
> This patch introduces APIs to bind guest PASID data to the assigned
> device entry in the physical IOMMU. See the diagram below for usage
> explaination.

explanation

Otherwise Looks fine to me. I was wondering if we would be able to reuse
the API for Arm SMMUv2, which allows nesting translation, but without
PASID - there is a single address space per device, with two stages of
translation. I think it would work, although it would look better with
something like "PGD" instead of "PASID" in the API names (e.g.
iommu_sva_bind_gpgd) since that case wouldn't use PASID at all. But I
don't want to quibble over names, so

Reviewed-by: Jean-Philippe Brucker <jean-philippe@...aro.org>